A prior art was proposed as Taiwan Patent No. M293121 “Screwdriver Bit Holder Structure (1)”, which comprises a screwdriver bit holder that has a polygon hole allowing load or unload of a driver bit, and at least a shaft-axis hole on top of it allowing balls to fit in; a ring clipped on the holder body externally, pushed by a spring component that is set between the ring and the holder body, and its inner part has a pressing wall used to push balls to fix bits. Its features include: at least one shaft-axis hole at the lower part of the holder body for balls to fit in, and a cylinder cavity at the inner part of the polygon hole. A spring component and fixing plate are set inside the cylinder cavity, and the fixing plate has a triangle recess facing the shaft-axis hole. The ring has a concave and a pushing surface facing the shaft-axis hole, and the pressing wall of it is gradient-curved surfaced. Based on aforementioned structure, the pushing surface of the ring can push balls into the triangle recess so as to position the ring and fixing plate, and then utilize the gradient-curved surfaced pressing wall to push balls fit into the concaves of driver bits for tightening.
Although driver bits can be fixed in the polygon hole tightly based on aforementioned structure, it may cause safety concern because the spring component fixed in the fixing plate will suddenly and fully release accumulated power, then pushes fixing plate move outwards rapidly, which further forces the magnetized bits to spring out of the bit holder too powerfully to a dangerous extent when the bits are released by pushing down the ring until the top and bottom balls can leave the concaves of the bits and the triangle recess of fixing plate.
Throughout rigorous tests and researches, the inventor finally devised such an improved structure that enables a driver bit to be unloaded from polygon hole more gently to prevent dangers from powerful ejection of the bit occurring in prior arts. Therefore, a patent application is hereby being filed based on the absolute novelty and capability of industrial application of the invention.